In the prior art, in the design of the rotor vanes and the stator vanes of a turbomolecular pump, a two-dimensional cross sectional vane shape like that shown in FIG. 2 has been investigated as a model. One guide when designing a vane is the dimensionless number X that is the ratio between the inter-vane distance S and the chord length C, and the exhaust performance depends upon this dimensionless number X.
In the prior art, when applying a two dimensional cross sectional vane model, the rotor vanes and the stator vanes are considered as being equivalent, and vane design is performed for both of them with the same design principle. As such design principle, for example, the method of executing the design so that the dimensionless number X becomes the same for all the stages, and the method of executing the design so that the dimensionless number for each of the vane stages changes linearly from the pump inlet side towards its outlet side, and so on are known (refer to Patent Document #1).